How Bitwarden Encrypts and Decrypts Secrets

As part of my efforts in reducing my dependency on Big Tech, I have been researching how to self-host my password manager. One solution that looks very promising is Vaultwarden, an open source clone of the Bitwarden cloud server. An interesting aspect of this server is that it stores all the secrets in a standard SQLite database, so in addition to having the self-hosted password server I could keep a backup copy of the database on my machine and query it directly. But of course, the secrets are encrypted in this database, so they are useless unless I learn how to decrypt them, similar to how the Bitwarden clients do it. Speaking of the Bitwarden clients, while I was writing this article it came out that the official Bitwarden CLI client was compromised in a supply chain attack. This is a tool that I personally use and have on all my computers, so this feels like a wake up call to me. Luckily I did not install the compromised version myself, but I think there is an argument to be made…